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used this bag for four days in Tassie a week ago. Sensational - so easy to open up and access gear withou having to remove. I bought it for use when on my bike but it proved its worth on the streets of hobart and in port arthur. very compact but fits lots of gear for a beginner like me (d70s, kit lens, 70 -300 ED, 50mm 1.4, full set of extension lens and my trust Sony DSC V1 plus all the extra bits in accompanying pockets. would easily fit a SB 600 or 800 removing one of the above)
bought mine from NZ on the net (AUS$130 inc P/H)..no doubt on sale for cheaper in Oz by now but I would highly recommend to those wanting to buy a really comfortable, versatile and life long bag. couldnt be happier with one of my first i/net purchases.
R2
Took lots of photos but still deciding on the 2 or 3 to post for critiqeuing here!!

I am thinking of this bag (like I need another, but anyway ....).

Do you think it would fit a fat wide angle lens when attached to my camera body (like my canon 17-40 - it takes 77mm filters)?

I am interested in one as a travel bag - so I would leave my big heavy lenses (70-200 2.8, 400 5.6) at home. I would take my 20D, 17-40 F4L, 100mm macro (same size as your 70-300), 20mm 1.8, and a flash - reckon it would fit okay?

How comfy is it to wear for a long period (ie, all day)?

the compartments are all velcro adjustable but you would loose a bit of flexibility with the 77mm filter but still should be able to accomodate the gear you mention. I'm no expert in these areas but have tried to find a link from Nikonians.com or dpreview.com that had a lot more info when I was looking.
I carried my fully laden bag around for a full day and found it pretty good - extra strap helps spread the load. It really served its purpose though - not having to take it off every time to change lenses etc is where the value is for a newbie like me.
hope this helps.
cheers
R2
this link may give you some extra info - http://www.lowepro.com/Products/Sling_B ... 00_AW.aspx